Solar Terrestrial Activity Report

Activity chart

Last major update issued on April 9, 2024 at 06:40 UT.

Charts (* = updated daily) Data and archive
  Solar wind (*) Solar and geomagnetic data - last month (*)
  Electron fluence (*) Archived daily reports and monthly data since 2003.01 (April 1, 2024)
Solar cycle Solar cycles 23-25 (April 1, 2024) Historical solar and geomagnetic data charts 1954-2006 (April 5, 2007)
  Cycle 24-25 progress (April 1, 2024) Noon SDO sunspot count 1K image / 4K (*)
  Solar cycles 1-24 (July 1, 2020) POES auroral activity level [October 2009 - December 2012]
  Comparison of cycles 21-25 (April 1, 2024) 3rd SSN Workshop, Tucson, 2013
  Comparison of cycles 12-14, 16, 24-25 (April 1, 2024) 4th SSN Workshop, Locarno, 2014
  Solar polar fields vs. solar cycles (March 3, 2024) Cycle 25 spots (final update December 25, 2019)
  Solar cycles 24-25 transition using 365d smoothing Research: Solar Cycle 25 Started on November 17, 2019 with 365 Days Smoothing
Calculating the Strength of Solar Cycle 25 Using 365-day Smoothing

Recent activity

The geomagnetic field was quiet to unsettled on April 8 under the influence of weak CME effects. The high latitude magnetometer at Andenes recorded quiet to active levels. The above 10 MeV proton flux was at background levels at the end of the day.

Solar flux density measured at 20h UT on 2.8 GHz was 124.8 - decreasing 5.7 over the previous solar rotation. (Centered 1 year average SF at 1 AU - 183 days ago: 156.95. In comparison SC24 peaked on June 28, 2014 at 145.50. Current SC25 peak: 158.71 on June 27, 2023). The Potsdam WDC planetary A index was 7 (STAR Ap - based on the mean of three hour interval ap indices: 7.4). Three hour interval K indices: 23320110 (planetary), 23321210 (Boulder), 34320210 (Andenes).

The background x-ray flux is at the class B3 level (GOES 16).

At the time of counting spots (see image time), spots were observed in 12 active regions using 2K resolution (SN: 195) and in 8 active regions using 1K resolution (SN: 108) SDO/HMI images.

Region 13628 [N07E02] was quiet and stable.
Region 13629 [N06W68] decayed slowly and quietly.
Region 13631 [N09W48] decayed slowly and quietly.
Region 13632 [N27E07] was mostly quiet and stable. C1 flare: C1.2 @ 04:17 UT
Region 13633 [S08E43] was quiet and stable.
New region 13634 [N27E55] rotated into view on April 7 and was numbered the next day by SWPC as the spot group began to decay. C1 flare: C1.4 @ 03:14 UT

Spotted regions not observed (or interpreted differently) by SWPC/USAF:
S9562 [N19W12] reemerged with tiny spots
S9570 [S15E15] was quiet and stable.
S9575 [S03E20] decayed slowly and quietly.
New region S9576 [N09E43] was observed with tiny spots in an old plage area.
New region S9577 [S17E42] was observed with tiny spots in an old plage area.
New region S9578 [N19E78] rotated into view with a tiny spot.

C2+ flares

Magnitude Peak time (UT) Location Source Recorded by Comment

Coronal mass ejections (CMEs)

April 6-8: No obviously Earth directed CMEs were observed.

Coronal holes

[Coronal hole history (since October 2002)]
[Compare today's report to the situation one solar rotation ago: 28 days ago 27 days ago 26 days ago]

A small positive polarity northern hemisphere coronal hole (CH1212) was Earth facing on April 4-5. A small negative polarity southern hemisphere coronal hole (CH1213) will likely rotate across the central meridian on April 9.

Propagation

Long distance low and medium frequency (below 2 MHz) propagation along paths north of due west over upper middle and high latitudes is poor to fair. Propagation on long distance northeast-southwest paths is poor.

Forecast

The geomagnetic field is expected to be quiet to unsettled on April 9 due to effects from CH1212. Quiet conditions are likely on April 10-11. Unsettled intervals are possible on April 12-13 due to effects from CH1213.

Coronal holes (1) Coronal mass ejections (2) M and X class flares (3)
     

1) Effects from a coronal hole could reach Earth within the next 5 days. When the high speed stream has arrived the color changes to green.
2) Effects from a CME are likely to be observed at Earth within 96 hours.
3) There is a possibility of either M or X class flares within the next 48 hours.

Green: 0-30% probability, Yellow: 30-70% probability, Red: 70-100% probability.

Active solar regions


(Click on image for 2K resolution). 4K resolution. Compare to the previous day's image.
0.5K image

When available the active region map has a coronal hole polarity overlay where red (pink) is negative and blue is positive.

Data for all officially numbered solar regions according to the Solar Region Summary provided by NOAA/SWPC, all other regions are numbered sequentially as they emerge using the STAR spot number. Comments are my own, as is the STAR spot count (spots observed at or inside a few hours before midnight) and data for regions not numbered by SWPC or where SWPC has observed no spots. SWPC active region numbers in the table below and in the active region map above are the historic SWPC/USAF numbers. SWPC data considered to be not sufficiently precise (location, area, classification) are colored red.

Active region SWPC date numbered
STAR detected
Spot count Location at midnight Area Classification SDO / HMI 4K continuum
image with magnetic polarity overlays
Comment
SWPC/
USAF
Magnetic
(SDO)
SWPC STAR Current Previous
2K 1K
13624 2024.03.30
2024.03.30
      N15W74          

location: N17W65

13630 2024.03.30
2024.04.05
      S11W67         location: S10W65
13631 2024.03.31
2024.04.05
1 2 1 N11W48 0010 AXX AXX location: N09W48

area: 0005

13629 2024.04.01
2024.04.04
3 9 3 N06W69 0020 CAO CRO

location: N06W54

13627 2024.04.01
2024.04.02
      N09W23        

location: N10W21

S9557 2024.04.01       N27W57            
S9560 2024.04.01       S07W46            
S9562 2024.04.02   10 3 N21W18 0020   BXO    
13628 2024.04.02
2024.04.03
5 15 7 N08W00 0260 CHO CKO

area: 0480

location: N07E02

13632 2024.04.03
2024.04.05
2 4 2 N28E04 0010 HSX HRX location: N27E07
S9567 2024.04.04       S26W32          
13633 2024.04.05
2024.04.06
6 15 10 S07E44 0160 DSI DSI location: S08E43

area: 0280

S9570 2024.04.05   4   S15E15 0006   BXO  
S9572 2024.04.06       N17W54            
S9573 2024.04.06       S50W40            
13634 2024.04.07
2024.04.08
2 5 1 N27E54 0010 AXX BXO location: N27E55

area: 0007

S9575 2024.04.07   4 1 S03E20 0006   BXO  
S9576 2024.04.08   3   N09E43 0003   AXX    
S9577 2024.04.08   3   S17E42 0006   BXO    
S9578 2024.04.08   1   N19E78 0001   AXX    
Total spot count: 19 75 28  
Sunspot number: 79 195 108  (total spot count + 10 * number of spotted regions)
Weighted SN: 44 96 49  (Sum of total spot count + classification weighting for each AR. Classification weighting: X=0, R=3, A/S=5, H/K=10)
Relative sunspot number (Wolf number): 87 107 86  

Monthly solar cycle data

Month Average solar flux International sunspot number
(WDC-SILSO)
Smoothed sunspot number (4) Average ap
(3)
Measured 1 AU
2014.02 170.3
(cycle peak)
166.3 146.1 (SC24 peak) 110.5 10.70
2014.04 143.9 144.8 112.5 116.4 (SC24 solar max) 7.88
2017.09 91.3 92.3 43.6 18.2 (-1.3) 18.22
(SC24 peak)
2019.11 70.2 68.7 0.5 2.0 (-0.6)
(Solar minimum using 365d smoothing:
November 17, 2019)
4.19
2019.12 70.8 68.6 1.6 1.8 (-0.2)
(ISN 13 months smoothed
solar minimum)
3.22
2022.09 135.1 136.5 96.0 96.5 (+3.9) 12.18
2022.10 133.5 132.7 95.5 98.9 (+2.4) 11.16
2022.11 123.4 120.7 80.5 101.2 (+2.3) 9.33
2022.12 147.9 143.4 112.8 106.7 (+5.5) 10.99
2023.01 182.4 176.6 144.4 113.3 (+6.6) 8.73
2023.02 167.2 163.2 111.3 117.8 (+3.5) 14.48
(current
SC25 peak)
2023.03 157.2 155.6 123.3 121.1 (+3.3) 14.42
2023.04 145.4 146.4 97.6 122.9 (+1.8) 13.40
2023.05 155.6 159.2 137.4 124.1 (+1.2) 10.67
2023.06 161.7 166.8 160.5 125.2 (+1.1)
(SC25 solar max candidate)
8.95
2023.07  176.4 182.2 160.0 124.3 (-0.9) 8.15
2023.08  153.7 157.6 114.8 124.0 (-0.3) 7.19
2023.09  154.4 156.0 134.2 123.8 (-0.2) 14.26
2023.10  142.8 141.9 99.4 (123.8 projected, 0.0) 8.16
2023.11 153.5 150.2 105.4 (123.5 projected, -0.3) 12.20
2023.12 151.1 146.4 114.2 (120.1 projected, -3.4) 9.60
2024.01 164.6 159.3 123.0 (116.8 projected, -3.3) 5.46
2024.02 172.5 168.3 124.6 (116.0 projected, -0.8) 5.31
2024.03 154.4 152.9 104.9 (115.4 projected, -0.6) 11.1
2024.04 118.9 (1)   16.2 (2A) / 60.9 (2B) / 115.6 (2C) (115.4 projected, -0.0) (8.2)
2024.05       (116.6 projected, +1.2)  
2024.06       (115.8 projected, -0.8)  
2024.07       (114.1 projected, -1.7)  
2024.08       (112.1 projected, -2.0)  
2024.09       (110.9 projected, -1.2)  
2024.10       (110.3 projected, -0.6)  

1) Running average based on the daily 20:00 UTC observed solar flux value at 2800 MHz and any corrections applied to that measurement.
2A) Current impact on the monthly sunspot number based on the Boulder (NOAA/SWPC) sunspot number (accumulated daily sunspots / month days).
2B) Boulder SN current month average to date.
2C) STAR SDO 1K Wolf number 30 day average.
3) Running average based on the quicklook and definitive Potsdam WDC ap indices. Values in red are based on the definitive international GFZ Potsdam WDC ap indices.
4) Source: WDC-SILSO, Royal Observatory Of Belgium, Brussels

Solar cycles 24-25

Smoothed SF and sunspot numbers

Update on the progress of solar cycle 25 as of March 10, 2024

Solar activity saw a significant decrease during the latter half of February and the first part of March. While there is still a chance that there could be another and higher peak in October or November 2023, chances that June 2023 was solar max has increased. After November 2023 there is currently no other obvious candidate solar max month. Taking into account the state of the solar polar fields another major peak during SC25 is becoming less likely.

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This report has been prepared by Jan Alvestad. It is based on the analysis of data from whatever sources are available at the time the report is prepared. All time references are to Universal Time. Comments and suggestions are always welcome.

SDO images are courtesy of NASA/SDO and the AIA, EVE, and HMI science teams.